The methods for checking modules are taken from the ceph-mon
charm and charmhelpers.contrib.storage.linux.ceph module. When
this lands I'll update the ch methods to emit a deprecation warning
and update the ceph-mon charm to use these methods instead.
Change-Id: I1b7f08c3bd94828a5c6468df7aab6b38517cf3fa
Helper functions for the ceph charms. This library has shared functionality that is used in the ceph-mon, ceph-osd and ceph
charms. Anything that needs to be shared across the ceph charms should live here.